Patella Fractures

Mechanism of Injury

The patella may fracture as a result of direct or indirect trauma. The former includes a fall onto the knee or hitting the dashboard of a car in a road traffic accident. Indirect trauma may occur from sudden contraction of the quadriceps muscle as in stumbling or jumping.

Classification

These fractures can be classified according to the mechanism of injury or the fracture pattern: transverse, oblique, stellate or comminuted and longitudinal or marginal.

Clinical Features

The history generally suggests the injury. The knee is painful and swollen. On examination, the patella is tender and the separation of the fragments may be felt.

X-rays confirm the diagnosis with two views being needed: AP and lateral. The latter outlines the patella and shows any displacement. Occasionally a sky-line view may be required.

Associated Injuries

An intact quadriceps mechanism should be sort as it may be damaged. This is performed by asking the patient to lift a straight leg.